Global warming is far from a rec­ent phenomenon – it devastated the Earth 300million years ago, scientists revealed.

Climate change was behind the des­truction of vast areas of the planet’s first rainforests, analysis of deposits found in the US show.

The change saw primitive, weedy ferns abruptly replace ‘towering club-moss rainforests’, said Dr Howard Falcon-Lang of Bristol University. The finding follows new research into huge ‘fossil forests’ found in Ill­inois coal mines three years ago.

One preserved patch covered 10,000 hectares (25,000 acres) – the size of a city. ‘It was a truly amazing exper­ience. We explored underground mines on foot and discovered spectacular fossils by the light of our lamps,’ said Dr Falcon-Lang.

These first rainforests evolved when the US lay on the Equator.

The Earth then went through an int­ense period of global warming which led to a ‘dramatic collapse’ in the vegetation, he added.

Understanding how this happened could help us avert a similar disaster, said the scientist, who presented his findings at the BA Festival of Science in Liverpool yesterday.

Further research into how and why the extinction happened is expected over the next five years.